1. Field of the Invention
The invention relates to test devices and, more particularly, to a test device for static and dynamic testing of workpieces.
The invention relates to a test device for the static and dynamic testing of workpieces, having a first, fixed clamping device and a second, movable clamping device for the workpiece, and a drive for moving the second clamping device, where the drive has a rocker on which the second clamping device is mounted in a rotatable manner, and the two ends of the rocker are each connected to a rotatably mounted connecting rod, and the free ends of the connecting rods are each coupled to a crank mechanism.
The test machine is based on the principle of the generation of a stroke by means of a crank mechanism. Since the stroke has to be controlled continuously during operation for some component tests and therefore must be adjustable, a simple means of adjustment during running operation, which in addition is as far as possible free from wear, is necessary.
A means of adjusting the amplitude during operation is known from GB450,347. In this device, a rocker is driven by two cams. Adjustment of the phase position of the cams with respect to one another gives rise to different strokes, from 0 to twice the throw of the cams. A disadvantage in this arrangement is the necessity for slide blocks. These have to support the counterpressure, and are at the same time subject to a significant relative movement during each stroke, meaning that high wear can be expected.
2. Discussion of the Prior Art
This problem of the basic principle was recognized, for example, in FR1388925 and overcome by making the connection to the rocker by means of two connecting rods. However, this mechanism has the disadvantage that it is not possible to produce strokes which are as small as desired therewith. This is necessary on the one hand for “starting” a test machine, since otherwise it may not be possible to apply the required drive energy of the drive in order to subject the sample to the desired load, and on the other hand the smallest possible stroke may already be so large that it overloads the sample.
The problem of a stroke which cannot be set to zero has been solved by DE2900373C3 by using a total of four further connecting rods or push rods. Although this enables the stroke to be reset to zero, a special geometrical matching of the dimensions is necessary for the principle shown. The large number of joints and components used (and thus of the masses moved) means that the principle appears of little suitability for a cyclic application which is intended to be operated for many years without play and wear.